The complex healing process can be divided into 3 to 5 phases, depending on whether or not haemostasis is included in the inflammatory phase and wether the re-epithelialisation phase is included in the proliferative stage. Furthermore, these different phases overlap with one another, to a certain degree. However, all the different phases overlap with one another.

THE PROLIFERATIVE PHASE can begin quickly with the proliferation of endothelial cells and fibroblasts to lead to the formation of new blood vessels (angiogenesis) and the synthesis of a new extracellular matrix (ECM). As the new ECM is re-modelled, the existing matrix is degraded by a number of Proteases, enzymes known as Matrix Metalloproteinase’s (MMP’s); MMP’s help with autolytic debridement (cleansing) of the wound, and cell migration. Their levels increase within the wound after injury & decrease when the wound is bacteria free. The fibroblasts then acquire the morphology and biochemical characteristics of smooth muscle cells to become myofibroblasts. This essential differentiation phenomenon takes place under the influence of cytokines and growth factors released during the previous phase. The myofibroblasts are the main cells responsible for synthesis of the extracellular matrix and contribute to reorganisation of this matrix as the wound contracts. The extracellular matrix plays an important controlling role because some factors may be stored in latent form and activated when they are released. Re-epithelialisation occurs to close the wound with the migration of epithelial cells starting from the edges of the wound and skin appendages. Differentiation of keratinocytes then helps to restore the barrier function of the epidermis.